The specific objective of the proposed research is to try to understand how 5-iodo-2'-deoxyuridine (IdUrd) increases alkaline phosphatase activity in the human cancer cell line, HeLa. Studies will be continued in which antibody made against the purified enzyme will be used to titer the synthesis of alkaline phosphatase molecules in control and IdUrd treat cells to determine if the increased enzyme activity reflects an increase in the synthesis or in the catalytic efficiency of the enzyme. Alkaline phosphatase will be purified from control and IdUrd treated cells for phosphorous analysis to ascertain if, as is the case after hydrocortisone induction, there is a decrease in phosphorous content of the induced enzyme. For reasons outlined in the text, protein kinase activity will be compared in control and IdUrd treated cells. Further studies will be done to ascertain how xanthine derivatives prevent induction of alkaline phosphatase activity by IdUrd and cyclic-AMP concentration will be measured to determine if this compound has a role in this effect. The relation between IdUrd substitution of DNA and enzyme induction will be further analyzed by cot analysis and nuclease digestion of DNA to see if certain subclasses of DNA are preferentially substituted for induction. Lastly, procedures outlined in the text will be used to measure alkaline phosphatase mRNA or alternatively the mRNA synthesis of another protein that may be involved in alkaline phosphatase enzyme induction will be determined.